Dissolved black carbon induced elimination of bisphenol a by peroxymonosulfate activation through HClO mediated oxidation process

Abstract

Dissolved black carbon (DBC) is released into environmental media following the wide adoption of biochar-catalyzed peroxymonosulfate (PMS) advanced oxidation processes (AOPs) in wastewater treatment. However, the possible reactivity between DBC and PMS in the process has not yet been reported. In this study, the role of DBC in the biochar-initiated PMS activation process was comprehensively explored. For the first time, we discovered that DBC could significantly improve the oxidation of bisphenol A (BPA) by PMS activation with a pseudo-first-order kinetic rate constant (kapp) of 0.040 min−1. Different biomass feedstocks led to distinguishable kapp values, revealing the reactive species were largely depended on the intrinsic properties of biomass. The activation mechanism was comprehensively elucidated through in-situ and ex-situ techniques. Radical species (i.e., •OH and SO4•−) as well as singlet oxygen (1O2) were not the dominant contributors, while the Cl- induced formation of hypochlorous acid (HClO) was confirmed to be the primary oxidative species responsible for BPA oxidation. On the other hand, dissolved organic components in DBC preferentially consumed HClO and thus inhibited the oxidation of BPA. Typical chlorinated derivatives (i.e., 3-chlorobisphenol A, 3,3′-dichlorobisphenol A, 3,5-dichlorobisphenol A and 3,3′,5- trichlorobisphenol A) were identified after the oxidation process. These findings benefited further understanding of the role of biochar derived DBC and revealed the potential environmental risk of biochar-activated PMS oxidation processes.